Heating furnace



Feb. 13, 1934. l.-.HARTER HEATING FURNACE Filed Oct. 6, 1932 3 Sheets-Sheet l INVENTOR a L; ATTORNEY l. HARTER HEATING FURNACE Feb. 13, 1934.

Filed' Oct. 6, 1952 3 Sheets-Sheet 2 INVENTOR M A; ATTORNEY HEATING FURNACE Filed 001;. 6, 1932 3 Sheets-Sheet 5 -INVENTOR 9 4-; ATTORNEY Patented Feb. 13, 1934 UNITED STATES PATENT OFFICE? 1,940,971 ammo muses Isaac Barter, New York, N. Y., assignor to The Babcock & Wilcox Tube Company, West Mayfleld, Pa, a corporation of Pennsylvania Application October 6,

14 (flaims.

relatively low, and which shall be highly efllcient and therefore economical to operate, shall be capable of heating the articles to temperatures even of the highest industrial range without harm to the parts of the furnace structure, and may be heated up to working temperature in an extremely short time, and in passing through which the articles being heated will be protected against oxidation.

Apparatus according to the invention comprises a plurality of furnace units, most desirably a series of three or more, mounted end to end and spaced a short distance apart, and conveyor rolls for supporting and feeding the article being heated mounted between the furnace units and adjacent the outer ends of the end units. The

furnace units have an opening in each and sub--.

stantially larger than the transverse dimensions of the article to be heated so that the articles, supported by the conveyor rolls, will pass through the openings without objectionable contact and so that combustion gases may escape from the furnace chambers through these openings about the articles. The articles as they pass from one furnace unit to another will thus be surrounded by an atmosphere of hot substantially inert gases by which the articles will be protected against wastage by oxidation. Such blanketing of the articles between the furnace units by the hot gases also has the effect of greatly reducing the loss of heat by radiation as the articles move between the furnace units, and the interposed conveyor rolls being also heated by the escaping gases, there will be but slight loss of heat by conduction. The conveyor rolls, although heated to a comparatively high temperature by the escaping gases, will not be subjected to the full temperature of the furnace chambers, and temperatures may thus be maintained in the furnace chambers way above what would be possible if conveyor rolls were located within the chambers.

Covers are desirably provided over the conveyor rolls between the furnace units which serve to prevent upward dissipation of the combustion gases, thus securing more complete protection of the articles against access of air, and also by 1932. Serial No. 636,433 (Ci. 263-6) directing the gases downward serve to maintain the articles and the conveyor rolls at a higher temperature.

The size of the furnace units will, of course, depend on the size of the articles to be heated. They are relatively, short, being of less length than the articles to be heated and in no case longer than will permit of the articles to be heated being properly supported by the conveyor rolls located at the ends of and outside the furnace units. The furnace units are most desirably of cylindrical shape set with their longitudinal axes horizontal and provided with means for projecting heating flames tangentially into the furnace chamber, the escape for the products of combustion being through the end openings through which the articles to be heated are passed into and out from the furnace chamber. The combustion supporting air or oxygen is either pre-mixed with the fuel or supplied to the flame opemngs.

The furnace units are in some cases most desirably independently controlled so that different units will operate at different temperatures. With such control and with suitable control of the rate of feed of the articles through the furnace, the furnace may readily be adapted to heating or cooling cycles appropriate to a great variety of metals. The conveyor rolls are in most cases desirably skewed sufliciently to cause the work to be rotated slowly as it is advanced through the furnace units. This serves to prevent sagging of the work at temperatures and with spans between the conveyor rolls such that sagging would otherwise take place, in addition to serving the usual purpose of turning the work to secure uniform heating.

The drawings illustrate a multiple unit furnace according to the invention for heating rods, bars or tubes. In said drawings:-

Fig. 1 is a view in side elevation, and Fig. 2 is a plan view, of a part of the furnace, showing three furnace units and part of another, parts, including the fuel supply piping, being omitted from Fig. 2 and this figure showing the furnace without covers over the conveyor rolls;

Fig. 3 is a vertical sectional view on a larger scale of a portion of the furnace, showing one of the furnace units and part of an adjacent unit in section and a part of another unit in elevation, and the interposed conveyor rolls and roll covers;

Fig. 4 is a transverse section through one of the furnace units on line 4-4 of Fig. 3 and showing also the, fuel supply piping for the unit;

Fig. is a detail section taken on line 5-5 of Fi 3;

Fig. 6 is a sectional view similar to Fig. 4 but taken on line 6-6 of Fig. 3 and showing the mounting and driving connection for one of the conveyor rolls;

Fig. 7 is a detail view showing a skewed conveyor roll.

Referring to the drawings, the furnace comprises a plurality, for example, ten or twelve, of cylindrical furnace units 10 mounted end to end and spaced a short distance apart. Each unit has an opening 11 in each end substantially larger than the transverse dimensions of the articles to be heated, and in each space between adjacent units a driven conveyor roll 12 is mounted in position to support the article being heated and advance it endwisa through the furnace units. A similar conveyor roll is provided adjacent the outer end of each end furnace unit, one such roll being shown at the right hand end of Fig. 2. Each roll 12 is carried by a transverse shaft 13 mounted in bearings 14 and the roll shafts are driven from a longitudinal drive shaft 15 through bevel gears in the usual manner and as indicated by dotted lines in Fig. 6. In order to prevent the articles being heated from sagging betweenthe conveyor rolls because of the temperature to which they are heated and the length of the span between the rolls, the rolls, instead of being mounted with their axes at right angles to the line of travel of the articles, may be set slightly oblique, or skewed, as shown by Fig. 7, to cause the articles to be rotated slowly as they are advanced. This not only serves the usual purpose of so mounting furnace conveyor rolls of securing uniform heating of the articles, but also serves to prevent the articles from sagging at temperatures and with spans between the conveyor rolls such that sagging would otherwise take place.

The furnace units are made of suitable refractory material to withstand the desired high temperatures. Most desirably, and as shown, each unit comprises a-cylindrical shell of sheet metal having at each end an inwardly extending flange, or annular end plate, 21, and a main furnace body made up of a cylindrical outer body portion 22 of porous insulating refractory material next to the shell, and an inner cylindrical lining 23 of a high grade of firebrick or other suitable dense non-insulating heat absorbing refractory material, and end portions 24 of the same material as the inner lining 23. These end portions are best made up each of four quadrants 24a, 24b, 24c and 3 24d, as shown in Fig. 5. These quadrants are formed with flanges to extend about and provide seats for the ends of the inner firebrick lining 23, and the quadrants are shaped to provide when set in place the central opening 11 for entrance of the article to be heated at one end of the furnace unit and for exit of the article at the other end. The metal shell 20 is made with its end portion at each end separable from the main cylindrical portion of the shell, as by having each end portion provided with an outwardly extending flange 25 at its inner edge secured by bolts 26 as shown in'Fig. 6 to a flange 27 on the adjoining end of the main portion of the casing. Either end portion of the casing may thus readily be removed for renewal or repair of the refractory body portion. i 1

Each furnace body is provided with one or more, preferably two, tangential burner openings 30 through which the heating gas or oil flamesmay be projected into the furnace chamher. As shown in the drawings, the furnace units are equipped for gas heating by means of an explosive mixture of gas and air projected from a suitable discharge nozzle into the burner openings 30 which serve as flame maintaining tunnels. The gas is supplied through a. pressure main 31 from which a. branch supply pipe 32 leads upward for each furnace unit to supply gas for discharge into a Venturi mixing device 33 in which the gas is mixed with air drawn in by the energy of the gas and from which the mixture of gas and air in the desired proportions, usually proportions to maintain a reducing atmosphere in the furnace chamber, passes through branch pipes 34 and 35, each of which is connected to supply a discharge nozzle set to discharge into one of the burner openings 30. The branch pipe 32 for each furnace unit is provided with a control valve 36, and each pipe 32 is provided with a pressure gage 3'7 for showing the pressure under which the gas is being discharged into the Venturi mixing tube 33, thereby indicating the amount of gas being burned. By adjusting the valves 36, the heat of each furnace unit may be varied as desired, and the gages 3'7 will indicate the amount of gas being burned in each furnace unit and the relative amounts for the different units of the furnace.

The only outlets from the furnace chambers for the products of combustion are the end inlet and outlet 'openings 11. These openings, as stated, are of a size sufficiently larger than the transverse dimensions of the articles to be heated to provide space about the articles as they pass through the openings for escape of the products of combustion. The conveyor rolls 12 are set to support the rod or tube or other article being heated so that it is about centered in the openings 11 through which it is being advanced. The hot products of combustion flowing out through the end openings will thus completely surround that part of the article which is between the furnace units and will prevent, or substantially prevent, access of air to the article as it passes between adjacent furnace units from one to the other. Besides so protecting the article from oxidation in its passage between the furnace units, the hot gases prevent any substantial loss of heat by the article by radiation in its passage between the furnace units, and also maintain the conveyor rolls at a suitably high temperature so that there is a minimum of loss of heat through contact of the article with the rolls.

In order to secure the fullest possible protection of the articles in their passage between the furnace units, covers 40 are provided set between the furnace units over the space between the openings 11 in the ends of the units. These covers may be formed of firebrick or other suitable refractory material and are best of approximately half cylindrical shape and supported on shoulders 41 formed on the end portions 24 of the furnace bodies. As shown by Fig. 5, the shoulders 41 have lugs 42 for engaging the covers so as to hold them against angular displacement. The covers are most desirably set, as most clearly 1 shown by Fig. 5, so that the longitudinal edge of the cover at one side is at a lower level than the longitudinal edge at the other side. When the furnace is, as shown in Fig. 2, without the covers 40, the combustion gases escaping through the openings 11 tend to rise, creating an up-draft, so that unless the furnace units are sufficiently close together and the combustion gases are in suiiicient volume to completely envelope the article under such condition, air is liable to have access to the article from below. The covers prevent the gases from so rising and insure cornplete envelopment and protection of the article by the gases and also largely reduce the loss of heat by radiation from the article and cause the conveyor rolls to be kept at a desirablyhigh temperature, which, however, is substantially less than the temperature within the furnace chambers.

. The furnace units may be mounted in any suitable manner. As shown, each unit rests on two skeleton saddles which in turn rest on longitudinal girders 51 on a suitable foundation 52. Each unit is secured in position on its saddles 50 by means of a swing bolt 53 extending from a bracket on one of the saddles 50 and engaging a bracket on the bottom of the furnace unit. To releasea furnace unit so that it may be removed from its setting, it is only necessary to remove the covers 40 at each end of the unit and loosen the nut of the bolt 53. The furnace unit may then be lifted from its saddles. And in replacing the unit it is positioned on its saddles and then secured by swinging up the bolt 53 and tightening its nut. The roll shaft bearings 14 are conveniently mounted on a pair of girders 55 supported by spaced box supports 56.

The furnace units may obviously be of other shape and construction from that shown, and the size of the units and the number of units in the furnace and the shape of the inlet and outlet openings may vary according to the kind and size of articles to be heated and the temperatures to which the articles are to be heated and any particular heating or cooling cycles to which they are to be subjected. In a furnace such as shown by the drawings intended for heating metal tubes up to about 3 inches in diameter to comparatively high temperatures, the furnace units may have an outside length of about 4 ft. and diameter of about 2 ft., with the heating chamber about 14 inches in diameter and the inlet and outlet openings about 5 inches in diameter; and the units may be set to leave a space of about 9 inches between the faces of the end flanges 21. The length of the units will be limited by the permissible span between conveyor rolls, and this span length will, of course, vary according to the cross-sectional shape and size of the articles being heated, the material of which they are made, and the temperatures to which they are to be heated.

In using the term end and end wall" in the claims I have considered the ends of the furnace units to be the portions or walls of the unit which are opposite each other in the direction of the length of the multiple unit furnace .as a whole, whether the units are longer than they are wide or not.

What is claimed is:

1. A heating furnace, comprising a plurality of direct heating furnace units mounted end to end in spaced relation, and conveyor rolls between the furnace units outside the heating chambers, the furnace units being formed for the passage therethrough of the articles to be heated supported by the conveyor rolls and to discharge hot substantially inert gases from the furnace chambers to envelope the articles as they pass between the furnace units.

2. A heating furnace, comprising a plurality of direct heating furnace units mounted end to end in spaced relation, and conveyor rolls between the furnace units outside the heating chambers,

each furnace unit having an opening in each end for the passage of the articles being heated large enough to permit the articles to pass through without contact and furnace gases to escape. and the furnace units being so closely spaced that the articles being heated as they passbetween the furnace units will be surrounded by the gases escaping from said openings.

3. A heating furnace, comprising a plurality of direct heating furnace units mounted end to end in spaced relation, and conveyor rolls between the furnace units outside the heating chambers, the furnace units being of less length than the articles to be heated and each being provided with means for projecting a heating flame into its heating chamber and having an opening in each end for the passage of the article being-heated, the opening in the furnace unit ends which face another furnace unit being large enough, to permit escape of furnace gases about the articles as they pass between the furnace units, the heating chambers being otherwise closed.

4. A heating furnace, comprising a plurality of direct heating furnace units mounted end to end in spaced relation, and conveyor rolls between the furnace units outside the heating chambers, the furnace units being of less length than the articles being heated and formed to provide a cylindrical heating chamber and provided with means for projecting a heating flame tangentially into the heating chamber, and each furnace unit having an opening in each end for the passage of the articles being heated, the opening in the furnace unit ends which face another furnace unit being large enough to permit the escape of furnace gases about the articles as they pass between the furnace units, the heating chambers being otherwise closed.

5. In a heating furnace, comprising a plurality of direct heating furnace units mounted end to end in spaced relation, and conveyor rolls between the furnace units outside the heating chambers,

a furnace unit having an opening in each end for the passage of the articles being heated large enough to permit the articles to pass through 11) without contact and furnace gases to escape about the articles as they pass into and from the furnace unit.

6. A heating furnace, comprising a plurality of direct heating furnace units mounted end to end in spaced relation, and conveyor rolls between the furnace units outside the heating chambers, each furnace unit having an inlet and an outlet opening in opposite end walls for the passage of the articles being heated, and at least two of In said units having the openings in their facing end walls large enough to permit furnace gases to escape therethrough about the articles being heated as they pass between said two units, and said two units being so closely spaced that the 35 gases escaping from said openings will provide a protective atmosphere about the articles as they pass between the units.

7. A heating furnace, comprising two direct heating furnace units mounted in spaced relation, 1 and conveyor rolls between the furnace units outside the heating chambers, each of said furnace units having inlet and outlet openings for the passage of the article being heated, the openings in the two units being in alignment and the openings in the facing walls of the units being large enough to permit the furnace gases to escape about the articles as they pass between said units, and the units being so closely spaced that the gases escaping from said openings will pro- 50 vide aprotective atmosphere about the articles as they pass between said units. a

8. A direct heating furnace unit for a multiple unit heating furnace, said unit being provided with means for projecting a heating flame into its heating chamber and having inlet and outlet openings for the articles to be heated in opposite walls of the unit, said openings being large enough to permit furnace gases to escape about the articles being heated as they pass intoand from the furnace unit, the heating chamber being otherwise closed.

- Y 9. A heating furnace, comprising a plurality of direct heating furnace units mounted end to end in spaced relation, and conveyor rolls between the furnace units outside the heating chambers, each furnace unit being provided with means for projecting a heating flame into its heating chamber and having an opening in each end for the passage of the articles being heated, the opening in each furnace unit end which faces another furnace unit being large enough to permit the escape of furnace gases about the articles as they pass between the furnace units, the heating chambers being otherwise closed, and means for retarding dissipation of the furnace gases from the articles passing between the units.

10. A heating furnace, comprising a plurality of direct heating furnace units mounted end to end in spaced relation, and conveyor rolls between the furnace units outside the heating chambers, each furnace unit being provided with means for projecting a heating flame into its heating chamber and having an opening in each end for the passage of the articles being heated, the opening in each furnace unit end which faces another furnace unit being large enough to permit theescape of furnace gases about the articles as they pass between the furnace units, the heating chambers being otherwise closed, and covers bridging the space between the ends of adjacent furnace units over the conveyor rolls.

11. A heating furnace, comprising a plurality of direct heating furnace units mounted end to end in spaced relation, and conveyor rolls between the furnace units outside the heating chambers, each furnace unit being provided with means for projecting a heating flame into its heating chamber and having an opening in each end for the passage of the articles being heated, the opening in each furnace unit end which faces another furnace unit being large enough to permit the escape of furnace gases about the articles as they pass between the furnace units, the heating chambers being otherwise closed, and semi-cylindrical covers of refractory material bridging the spaces between the ends of adjacent furnace units over the conveyor rolls.

12. A heating furnace, comprising two direct heating furnace units mounted in spaced relation, and conveyor rolls between the furnace units outside the heating chambers, each of said units being provided with means for projecting a heating flame into its heating chamber and having inlet and outlet openings for the passage of articles being heated, the openings in the two units being in alignment and the openings in the facing walls of the units being large enough to permit the furnace gases to escape about the articles as they pass between said units, the heating chambers being otherwise closed, and covers bridging the space between the units.

13. A heating furnace, comprising a plurality of direct heating furnace units mounted end to end in spaced relation, and conveyor rolls between the furnace units outside the heating chambers, the furnace units being formed for the passage therethrough of the articles to be heated supported by the conveyor rolls and to discharge hot substantially inert gases from the furnace chambers to envelope the articles as they pass between the furnace units and each unit having means for controlling its fuel supply independently of the fuel supply of the other units.

14. A heating furnace, comprising a plurality of direct heating furnace units mounted end to end in spaced relation, and conveyor rolls between the furnace units outside the heating chambers mounted independently of the furnace units, the furnace units being formed for the passage therethrough of the articles to be heated supported by the conveyor rolls and to discharge hot substantially inert gases from the furnace chambers to envelope the articles as they pass between the furnace units and each unit being removable independently of the other units and independently of the adjacent conveyor rolls.

ISAAC HARTER. 

